Nanostructures assembled from thermoresponsive synthetic and biological polymers are widely applicable as sensors, electronic devices, molecular machines, drug delivery systems, and matrices for tissue engineering. The design features of these polymers, such as molecular composition, sequence, molecular weight, and aqueous solution concentration, permit tuning of the temperature at which phase transitions take place. Furthermore, it has been demonstrated that conjugates of thermoresponsive polymers provide a means of encoding dual thermal transitions; this multi-temperature responsiveness can be used to direct the assembly and disassembly of nanostructures at specific temperatures, increasing their potential range of applications. However, there is a lack of fundamental understanding of how the molecular design of these thermoresponsive conjugates affects the molecular interactions that drive the multi-step nanostructural assembly and disassembly processes. Developing such an understanding is key to expanding thermoresponsive nanostructures in applications such as biochemical sensors, actuation, molecular cargo (e.g., drug) delivery, and spatiotemporally controlled catalysis. The ability to characterize conjugates during nanostructure (dis)assembly using small-angle X-ray and neutron scattering coupled to advanced computational methods for analyzing the scattering results will provide transformative opportunities in molecular design.

The overarching objective of this proposal is to develop new approaches to interrogate molecular interactions, packing, and dynamics during the assembly and disassembly of technologically useful thermoresponsive conjugates. The research team has introduced dually thermoresponsive elastin-like peptide conjugates tethered to rod-like, oligomeric peptide domains. These molecules will be synthesized and characterized via X-ray and neutron scattering and microscopy. Experiments will be coupled to a new, coarse-grained model and simulations that will predict structural transitions with varying temperature for a range of molecular designs of the peptide conjugates. Temperature-controlled small-angle scattering experiments will probe structures at various temperatures in the assembly pathway. The intermediate structures, and potentially the final assembled structures, will not necessarily obey canonical structure and form factors, thus new computational methods that will elucidate the molecular underpinnings of the assembly process will be developed. The proposed work will leverage the knowledge gained from previous successful collaborations between the senior members of the research team. Interdisciplinary training of students in experiments and simulations will be enriched through this collaboration; the technical advances made through the proposed work will be integrated into the classroom. The researchers will build on their historical commitment in recruitment and retention of students from under-represented minority groups, contributing to curricula and outreach from the secondary through graduate levels.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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University of Delaware
United States
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